Microbiological process for the production of hydroxylated pyrazine derivatives

ABSTRACT

Microorganisms, which are capable of growing with pyrazine as the sole carbon, nitrogen and energy source. These microorganisms hydroxylate pyrazine derivatives of general formula: ##STR1## to hydroxylated pyrazine derivatives of general formula: ##STR2## and the latter are accumulated in the growth medium.

BACKGROUND OF THE INVENTION

1. Field Of The Invention

The invention relates to new microorganisms, which grow with pyrazine,and hydroxylate pyrazine derivatives of the general formula: ##STR3##wherein R₁ means a hydrogen atom or a halogen atom and R₂ and R₃ are thesame or different and mean a hydrogen atom or a C₁ -C₄ alkyl group, butR₁,R₂ and R₃ do not all simultaneously mean hydrogen, as well as to aprocess for the production of hydroxylated pyrazine derivatives.

2. Background Art

Hydroxylated pyrazine derivatives are, for example, importantintermediate products for the production of methoxyalkylpyrazines.Methoxyalkylpyrazines are essential components of aromatic substances[Maga and Sizer, J. Agric., Food Chem., 21, (1973), pages 22 to 30].

So far, only chemical processes for the production of hydroxylatedpyrazines have been known, such as, the one described by Karmas andSpoerri, in J. Amer. Chem. Soc., 74, (1952), pages 1580 to 1584, inwhich, for example, 2-hydroxy-5-methylpyrazine is synthesized startingfrom methylglyoxal and glycinamide hydrochloride. But this process hasthe drawback that the product is greatly contaminated.

In addition, studies on the biological catabolism of 2-hydroxypyrazineare described in Matley and Harle, Biochem. Soc. Trans., 4, (1976),pages 492 to 493.

A biotechnological process for the production of regiospecifichydroxylated pyrazine derivatives, starting from substituted pyrazinederivatives with microorganisms, which grow with pyrazine, is not known.

BROAD DESCRIPTION OF THE INVENTION

The main object of the invention is to provide new microorganisms, whichregiospecifically hydroxylate pyrazine derivatives of general formula Ieconomically in a biotechnological way and in a simple way, as well asto provide a biotechnological process for the production of hydroxylatedpyrazine derivatives. Other objects and advantages of the invention areset out herein or are obvious herefrom to one skilled in the art.

The objects and advantages of the invention are achieved by themicroorganisms of the invention and the processes of the invention. Themicroorganisms of the invention are capable or growing with pyrazine asthe sole carbon, nitrogen and energy source and as substrate reactpyrazine derivatives of the general formula: ##STR4## wherein R₁ is ahydrogen atom or a halogen atom and R₂ and R₃ are the same or differentand are each a hydrogen atom or a C₁ -C₄ alkyl group, but R₁, R₂ and R₃are not all simultaneously hydrogen, to a hydroxylated pyrazinederivative of the general formula: ##STR5## wherein R₁, R₂ and R₃ havethe above-mentioned meaning, and the latter is accumulated in the growthmedium. The invention includes the microorganisms of the invention inthe form of biologically pure or substantially biologically purecultures thereof.

A preferred microorganism according to the invention is themicroorganism with the designation Agrobacterium sp. deposited in theDSM with the number 6136. The invention includes its descendants andmutants.

The invention includes a process for the production of hydroxylatedpyrazine derivatives using one of the invention microorganisms toconvert a pyrazine derivative of the general formula: ##STR6## whereinR₁ is a hydrogen atom or a halogen atom and R₂ and R₃ are the same ordifferent and are each a hydrogen atom or a C₁ -C₄ alkyl group, but R₁,R₂ and R₃ are not all simultaneously hydrogen, to a hydroxylatedpyrazine derivative of the general formula: ##STR7## wherein R₁ R₂ andR₃ have the above-mentioned meaning, and the concentrated product isisolated.

Preferably the active enzymes of the microorganism are induced withpyrazine. Preferably the reaction is performed with one-time orcontinuous addition of the substrate, so that the substrateconcentration in the culture medium does not exceed 20 percent (w/v).Preferably the reaction is performed at a pH of 4 to 10. Also,preferably, the reaction is performed at temperatures of 0° to 55° C.

The invention also includes the compound 6-Ethyl-2-hydroxypyrazine.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention, all microorganisms are suitable which usepyrazine as the sole carbon, nitrogen and energy sources and areselected according to usual microbiological techniques, e.g., from soilsamples, sewage treatment plants, earth, anthills and compost piles.Suitably, all gram-positive and gram-negative microorganisms can be usedwhich catabolize pyrazine and hydroxylate a pyrazine derivative ofgeneral formula I as a substrate in a hydroxylated pyrazine derivativeof general formula II and accumulate the latter in the growth medium.

A preferred microorganism is Agrobacterium radiobacter DRS 3 with DSM(German Collection of Microorganisms) no. 6136, which is designatedbelow, because of detailed identification data, as microorganismAgrobacterium sp. (DSM no. 6136). This strain was deposited on Sep. 7,1990 in the German Collection of Microorganisms (DSM) and Zellkulturen[Cell Cultures] GmbH, Mascherodeweg 1b, 3300 Brunswick/FRG.

    ______________________________________                                        Scientific description of Agrobacterium sp. (DSM no. 6136)                    ______________________________________                                        cell shape     rods     ADH            -                                      width micron   0.6-0.8  LDC            -                                      length micron  1.5-3.0  ODC            -                                      mobility       +        ONPG           +                                      gram-reaction  -        VP             -                                      lysis by 3% KOH                                                                              +        indole         -                                      aminopeptidase (Cerny)                                                                       +        NO.sub.2 from NO.sub.3                                                                       +                                      spores         -        denitrification                                                                              +                                      oxidase        +        phenylalanine- -                                      catalase       W        desaminase                                            growth                  lecithinase    -                                      anaerobic      -        urease         +                                      37/41° C.                                                                             -/-      Simmons citrate                                                                              -                                      pH 5.6         -        malonate       -                                      Mac-Conkey-Agar                                                                              +        ketolactose    -                                      SS-Agar        -        hydrolysis of                                         cetrimide agar -        starch         -                                      2% NaCl        -        gelatin        -                                      pigments       -        casein         -                                      nondiffusing   -        DNA            -                                      diffusing      -        Tween 80       -                                      fluorescing    -        Aesculin       +                                      pyocyanin      -        tyrosine       -                                      acid from (OF test)     catabolism                                            aerobic glucose                                                                              -        alkalization of                                                                              +                                      anaerobic glucose                                                                            -        litmus milk                                           gas from glucose                                                                             -        growth substance                                                                             -                                      acid from (ASS)         requirement                                           glucose        +        substrate utilization                                 fructose       +        acetate        +                                      xylose         +        adipate        -                                      ethanol        +        caprate        -                                      m-erylthritol  +        citrate        -                                      melezitose     -        glycolate      +                                      arabinoze      +        lactate        +                                      saccharose     +        laevulinat     -                                      cellobiose     +        malate         +                                      trehalose      +                                                              rhamnose       +                                                              dulcitol       -                                                              sorbitol       +                                                              glycerol       +                                                              malonate       -                                                              phenyl acetate -                                                              suberate       -                                                              sebacinate     -                                                              m-tartrate     -                                                              L-arabinose    +                                                              fructose       +                                                              glucose        +                                                              mannose        +                                                              maltose        +                                                              xylose         +                                                              fucose         -                                                              mannitol       +                                                              2-ketogluconate                                                                              -                                                              N-acetylglocosamine                                                                          +                                                              L-asparate     +                                                              L-serine       +                                                              L-glutamate    +                                                              L-histidine    -                                                              hydroxybutyrate                                                                              -                                                              betaine        +                                                              methylamine    -                                                              methanol       -                                                              ethanol        -                                                              ______________________________________                                    

For the process for the production of hydroxylated pyrazine derivativesa pyrazine derivate of the general formula I as substrate: ##STR8##where R₁ is a hydrogen atom or a halogen atom and R₂ and R₃ are the sameor different and are a hydrogen atom or a C₁ -C₄ alkyl group, but R₁, R₂and R₃ are not all simultaneously hydrogen is converted with themicroorganisms set out above to a hudroxylated pyrazine derivative ofgeneral formula II: ##STR9## in which R₁, R₂ and R₃ have theabove-mentioned meaning, and the concentrated product is isolated.Preferably, hydroxylated pyrazine derivatives are produced by thesemicroorganisms, wherein R₁ means a hydrogen atom or a chlorine atom andR₂ and R₃ are the same or different and are a hydrogen atom, a methylgroup or ethyl group, but R₁, R₂ and R₃ are not all simultaneouslyhydrogen.

Also, a new hydroxylated pyrazine derivative, 6-ethyl-2-hydroxypyrazine,was produced by these microorganisms.

Usually, the microorganisms are cultivated before the actual process(substrate reaction) in a medium containing a growth substrate. Thegrowth substrate pyrazine is used in an amount of 0.001 to 10 percent byweight, relative to the culture medium, preferably in an amount of 0.001to 5 percent by weight, relative to the culture medium.

The enzymes of the microorganism responsible for hydroxylation aresuitably induced by pyrazine. The compound used for induction either canbe present during the reaction of the pyrazine derivative (substrate) orthe feed of this induction compound can be stopped during the reaction.Preferably, the feed of the compounds used for induction is stoppedduring the reaction of the pyrazine derivative either by stopping thefeed or by centrifuging the cells.

Before adding the substrate, the cells are cultivated up to an opticaldensity of 100 at 650 nm, preferably up to an optical density of 10 to60 at 650 nm.

As a nutrient medium for the microorganisms, both for the cultivationand for the actual process, the media usual among experts can be used.Preferably, the medium is used whose composition is indicated in Table 1below.

Usually, the actual process is then performed with dormant cells.

The pyrazine derivative of general formula I can be fed as a substrateone-time or continuously to the cell suspension, preferably so that thesubstrate concentration in the culture medium does not exceed 20 percent(w/v). In particular, the substrate concentration does not exceed 5percent (w/v) in the culture medium.

The reaction is suitably performed in a pH range of 4 to 10, preferably6 to 8. Usually the reaction is performed at a temperature of 0° to 55°C., preferably at 20° to 40° C.

After a usual reaction time of 5 to 100 hours, the hydroxylated pyrazinederivatives can be isolated in the known way, for example, by extractionwith a suitable organic solvent. Suitably, the hydroxylated pyrazinederivatives are isolated by extraction with chlorinated organicsolvents, such as, chlorinated hydrocarbons or ethyl acetate.

EXAMPLE 1 Isolation of pyrazine-metabolizing microorganisms

Aerobic pyrazine-metabolizing microorganisms were concentrated in theA+N medium (Table 1) with the adding of 0.1 percent (w/v) of pyrazine asthe sole carbon and energy source. The general techniques for isolatingmicroorganisms are described, for example, in G. Drews,Mikrobiologisches Praktikum [Microbiological Workshop], 4th ed.,Springer Verlag, (1983).

As an inoculum, samples from the earth, sewage treatment plants, compostand anthills were used. The concentrations were cultivated in shakingflasks at 30° C. After inoculating three times in fresh medium, theconcentrations of the same medium were streaked by adding 16 g of agarper liter and were incubated at 30° C. After repeated streaking on agarmedium, pure cultures were able to be isolated.

                  TABLE 1                                                         ______________________________________                                        A + N Medium                                                                                       Concentration                                            Composition:         (m/l)                                                    ______________________________________                                        (NH).sub.2 SO.sub.4  2000                                                     Na.sub.2 HPO.sub.4   2000                                                     KH.sub.2 PO.sub.4    1000                                                     NaCl                 3000                                                     MgCl.sub.2.6H.sub.2 O                                                                              400                                                      CaCl.sub.2.2H.sub.2 O                                                                              14.5                                                     FeCl.sub.3.6H.sub.2 O                                                                              0.8                                                      pyridoxal-hydrochloride                                                                            10 · 10.sup.-3                                  riboflavin           5 · 10.sup.-3                                   nicotinic acid amide 5 · 10.sup.-3                                   thiamin hydrochloride                                                                              2 · 10.sup.-3                                   biotin               2 · 10.sup.-3                                   pantothenic acid     5 · 10.sup.-3                                   p-aminobenzoate      5 · 10.sup.-3                                   folic acid           2 · 10.sup.-3                                   vitamin B12          5 · 10.sup.-3                                   ZnSO.sub.4.7H.sub.2 O                                                                              100 · 10.sup.-3                                 MnCl.sub.2.4H.sub.2 O                                                                              90 · 10.sup.-3                                  H.sub.3 BO.sub.3     300 · 10.sup.-3                                 CoCl.sub.2.6H.sub.2 O                                                                              200 · 10.sup.-3                                 CuCl.sub.2.2H.sub.2 O                                                                              10 · 10.sup.-3                                  NiCl.sub.2.6H.sub.2 O                                                                              20 · 10.sup.-3                                  Na.sub.2 MoO.sub.4. 2H.sub.2 O                                                                     30 · 10.sup.-3                                  EDTANa.sub.2.2H.sub.2 O                                                                            5 · 10.sup.-3                                   FeSO.sub.4.7H.sub.2 O                                                                              2 · 10.sup.-3                                   ______________________________________                                         (pH of the solution was adjusted to 7.0)                                 

EXAMPLE 2 Reaction of 3-chloropyrazine to 3-chloro-2-hydroxypyrazineAgrobacterium sp.

Agrobacterium sp. DSM no. 6136 was cultivated in the A+N medium with 0.1percent (w/v) of pyrazine in a fermenter at pH 7 and a temperature of30° C. Then, the cells were centrifuged, resuspended again in the A+Nmedium and adjusted to an optical density of 10 at 650 nm. This cellsuspension was added in a shaking flask and mixed with 26 mmol of3-chloropyrazine per liter (0.3 percent w/v).

After an incubation of 8 hours at 30° C. in a shaking machine, 20 mmolof 3-chloro-2-hydroxypyrazine per liter, corresponding to a yield of 77percent, was detected.

EXAMPLES 3 to 5

Examples 3 to 5 were performed corresponding to Example 2 and aresummarized in Table 2. The position of the hydroxyl group was determinedaccording to the data of MacDonald, J. C., Bishop, G. C., Mazurek,Tetrahedron, 32, (1976), p. 655 ff.

                                      TABLE 2                                     __________________________________________________________________________                Conc. of the                                                                  heterocycle in %                                                                         Reaction time   Yield                                  Ex.                                                                              Substrate                                                                              (w/v) in the medium                                                                      in hours                                                                             End product                                                                            in %                                   __________________________________________________________________________    3  2-methylpyrazine                                                                       0.2        1      2-hydroxy-6-                                                                           50                                                                   methylpyrazine                                  4  2-ethylpyrazine                                                                        0.2        24     6-ethyl-2-                                                                             20                                                                   hydroxypyrazine                                 5  2,3-dimethyl-                                                                          0.2        10     2-hydroxy-5,6-                                                                         20                                        pyrazine                   dimethylpyrazine                                __________________________________________________________________________

What is claimed is:
 1. Process for the production of a hydroxylatedpyrazine derivative, characterized in that pyrazine derivative of theformula I as substrate: ##STR10## wherein R₁ is a hydrogen atom or ahalogen atom and R₂ and R₃ are the same or different and are a hydrogenatom or a C₁ -C₄ alkyl group, but R₁, R₂ and R₃ are not allsimultaneously hydrogen, is converted with the microorganismAgrobacterium sp. DSM 6136, a descendant thereof or a mutant thereof, ina culture medium to a hydroxylated pyrazine derivative of the formulaII: ##STR11## wherein R₁, R₂ and R₃ have the above-mentioned meaning,and the hydroxylated pyrazine derivative of the formula II is isolated.2. Process according to claim 1 wherein the active enzymes of themicroorganism are induced with pyrazine.
 3. Process according to claim 1wherein the reaction is performed with one-time or continuous additionor substrate, so that the substrate concentration in the culture mediumdoes not exceed 20 percent (w/v).
 4. Process according to claim 3wherein the reaction is performed at a pH of 4 to
 10. 5. Processaccording to claim 4 wherein the reaction is performed at a temperaturesof 0° to 55° C.
 6. Process according to claim 1 wherein the reaction isperformed at a pH of 4 to
 10. 7. Process according to claim 6 whereinthe reaction is performed at a temperature of 0° to 55° C.